Partial Derivatives With N-Variables

TranscendArcu
Messages
277
Reaction score
0

Homework Statement



Given F(x_1,x_2,...,x_i,...,x_n) = nth-root(x_1*x_2*...*x_i*...*x_n), how do I take the partial derivative with respect to x_i, where x_i is an arbitrary variable?

Homework Equations


The Attempt at a Solution



Would it just be:

(1/n)(x_1*x_2*...*x_i*...*x_n)^((1/n)-1)*(x_1*x_2*...*x_i-1*x_i+1*...*x_n)?
 
Physics news on Phys.org
You got it!
 
Alright, nice!

What I'd like to try to do with this problem is maximize F (the equation for the geometric mean) when it is constrained by G(x_1,x_2,...,x_n) = x_1 + x_2 + ... + x_n = c, where c is some constant. I can take the partial derivative of G with respect to x_i and get,

G_x_i = 1

But I don't really know if I am a) on the right track for this problem or b) how to proceed if I am on the right track. What should my next step be?
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
Back
Top